Presbyope individuals are mainly divided into two categories:                ametropic presbyopes, i.e. individuals having before their presbyopia, a visual defect, so-called ametropia, such as for example myopia, hypermetropia or astigmatism; and        emmetropic presbyopes, i.e. individuals not having before their presbyopia, any visual defect.        
The present invention still more particularly relates to a progressive ophthalmic lens intended for emmetropic presbyopes.
For compensating presbyopia, it is known how to use a unifocal convex lens or a progressive ophthalmic lens.
Unifocal convex lens is conventionally adapted to vision at a close distance, i.e. at a reading distance comprised between 20 and 40 cm, preferentially of the order of 33 cm. The dioptric values compensating presbyopia range from +0.75 to +3.50 diopters per half or quarter diopter, in order to take into account rapid development of presbyopia. Thus, the emmetropic presbyope is led to regularly changing his/her lenses depending on the development of this ocular disorder and, if a lens with a power of +0.75 or +1.00 diopter is sufficient for the emerging presbyope or individual at the beginning of his/her presbyopia, he/she will rapidly be forced to use increasingly convex lenses up to a value from +3.00 to 3.50 diopters.
If a unifocal lens provides clear vision for reading, it however considerably reduces the vision distance by a loss of depth of field and this all the more so since the convex value of the lens is high. Now because of the increasingly frequent use of computer instruments, emmetropic presbyopes also need a lens which provide them with clear vision at a so-called intermediate distance corresponding to a working distance from a computer screen; this intermediate distance, located beyond the close distance or aforementioned reading distance, is comprised between 40 and 90 cm, preferentially of the order of 50 to 80 cm.
Working with a computer often requires seeing at the same time an object at a close distance, such as for example a reading document and a keyboard located at a close distance, and an object at an intermediate distance, in this case the computer screen. In order to meet this dual need of vision at a close distance and at an intermediate distance, the emmetropic presbyope would have no other choice but to have two pairs of spectacles with a unifocal lens, one dedicated to close distance vision the other one dedicated to intermediate distance vision.
The multifocal progressive ophthalmic lens, notably known from document FR 2 683 642, is conventionally used for compensating presbyopia while allowing the wearer of a pair of spectacles to observe objects over a large distance range without having to remove his/her pair of spectacles. Such a lens comprises an aspherical face having:                a top vision region suitable for far distance vision, i.e. for vision at infinity notably useful for driving a motor vehicle, said region being located in the high portion of the lens;        a bottom region for close distance vision, suitable for reading, said region being located in the low portion of the lens; and        an intermediate region connecting the top vision region to the bottom vision region, a so-called intermediate vision region.        
Usually, the aspherical face corresponds to the front face of the lens, which is the face opposite to the wearer of the pair of spectacles, while the rear face of the lens, which is the face directed towards the wearer of the pair of spectacles, is of the spherical type. With this spherical face, it is possible to adapt the lens to the ametropia of the wearer, so that the multifocal progressive ophthalmic lens is generally defined by its aspherical surface. Such progressive lenses thus have the primary purpose of compensating ametropia of the wearer in the high portion corresponding to the top far vision region, but also presbyopia in the low portion, corresponding to the bottom close-distance vision region. The intermediate vision region of these progressive lenses is generally very narrow between the aforementioned bottom and top vision regions. In the present state of the art, it is noticed that progressive lenses impose to a wearer who is looking at a computer screen to raise his/her head and to aim in the said narrow intermediate vision region. This non-ergonomic position is source of discomfort for presbyopes.
The mounting in a spectacle frame of a pair of progressive multifocal ophthalmic lenses requires great accuracy and can only be achieved by one skilled in the art. The mounting can only be carried out after a series of conducted measurements which take into account the position of the frame on the face of the wearer. The accuracy in the positioning of the reference point (also called lens design reference point) in the frame is essential for such lenses.
The state of the art may also be illustrated by the teaching of the patent application FR 2 769 997. In this application, for compensating presbyopia, the use of a multifocal ophthalmic lens having an aspherical face having a substantially umbilical and vertical principal meridian of progression is provided and the reference point of which for close vision is located at about 10 mm under the geometrical centre of the lens. This particular lens thus has an optical centre for close vision under the geometrical centre with a spherical decrease from this point up to the top of the lens. This lens of the multifocal type, which also allows compensation of ametropia, cannot be simply mounted in a frame since it also requires certain measurements associated with the physiognomy of the wearer. The mounting can only be achieved by one skilled in the art.
From patent application FR 2 844 365, a spectacle lens is also known, having an aspherical face with a non-umbilical principal meridian of progression and including:                a central portion adapted for intermediate distance vision, notably for working with a computer, the average transmission power in this central portion being substantially constant;        a top portion located on an upper side of the central portion, the average transmission power decreasing in the this top portion; and        a bottom portion located on a lower side of the central portion, the average transmission power increasing in this bottom portion.        
This lens has the drawback of respectively providing two bottom and top portions which are very narrow. Thus, the narrow top region is detrimental to peripheral visual perception in proximity vision by a restricted lateral field.